1. Field of the Invention
The present invention relates to the technical field of backlight local dimming and, more particularly, to a method and apparatus of approximating backlight spread in a local dimming system.
2. Description of Related Art
Multiple backlight sources are typically used in a current liquid crystal display (LCD) device for controlling a plurality of display areas of the LCD device to save the power. The backlight local dimming indicates that the backlight sources of the LCD device are adjusted according to the image brightness, but not in a state of full brightness.
Typically, the backlight sources of the LCD device operate at full brightness. The display of a dark frame is achieved by reducing the transmittance of liquid crystal rather than the reduction of power consumption. By contrast, the backlight local dimming allows the brightness of backlight source to be varied with changed dark and light frames, so that the brightness of backlight source is reduced when a dark frame is displayed. Thus, the entire amount of power consumption relating to the backlight sources is reduced.
In addition to the power consumption reduction, the backlight local dimming can improve the frame quality of the LCD device. For example, the dynamic contrast is dramatically increased. In addition, the backlight local dimming can be applied in the backlight sources to further increase the number of gray scales on the LCD device.
According to the entire power consumption of an LCD device, the backlight module typically occupies the largest proportion, which is about 66%. Furthermore, the trend of LCD devices develops to a large size, and thus the frames to be displayed require higher brightness, which consume more power. From the viewpoint of power saving, the backlight local dimming can relatively reduce the amount of power consumption on the large LCD device. In addition, the increase on the frame quality provides the optimal solution for the current backlight sources.
A typical backlight local dimming can first generate backlight signals to provide the backlight intensity spread data, then perform a convolution operation on the backlight signals and the backlight intensity spread data, and finally generate LCD compensation signals in accordance with the data generated in the convolution operation. Namely, the prior art has to establish a light spread function (LSF) for obtaining brightness spreading of the pixels on the panel when the backlight sources are turned on. Next, the established light spread function convolutes the backlight values decided for the blocks to emulate the actual spreading of backlight intensities of the backlight sources. However, the light spread function of the backlight sources influences the entire display panel, and the amount of data is very large so that a relatively large of storage space is required for completing the convolution operation. Accordingly, such a complicated operation process in the prior art may cause high hardware cost and additional operation time.
To overcome this, another prior art uses a blurring process to obtain the light spread function. The blurring process uses a low pass filter (LPF) to operate the blurring and amplification for several times. However, the LPF also needs the complicated operation.
Therefore, it is desirable to provide an improved method and apparatus of approximating backlight spread in a local dimming system to mitigate and/or obviate the aforementioned problems.